Video security system

ABSTRACT

A video security system (10) capable of monitoring and recording fixed and moving targets and recording management information into a video signal such that the text can be removed from the video image produced by the video signal at playback of the recorded video signal. The VSS (10) allows a camera (70b) to switch (toggle) between two or more view positions of interest and to set the view positions into memory by pressing a single switch. The cameras (70b) are controlled to move rapidly, but accurately, between the positions within controlled parameters of speed and acceleration--including a period of substantially zero acceleration between changes in the rate of acceleration.

This is a division of application Ser. No. 08/750,921, filed Jan. 22,1997, now U.S. Pat. No. 5,745,166 which is a 371 of PCT/AU 95/00457 fileJul. 26, 1995.

FIELD OF THE INVENTION

The present invention relates to a video security system particularly,although not exclusively, envisaged for use in the monitoring of aplurality of locations, such as, in a building, for example, a casino.

More particularly the present invention relates to a video securitysystem (VSS) particularly directed at addressing the difficulties whichprior art security systems generally experience, such as:

1. avoiding text information obliterating important video information;

2. switching repeatedly between two or more views of interest with asingle camera;

3. dealing with equalisation problems between video cameras, videomonitors and/or VCRs or other video signal recording device;

4. overcoming the problem of tracking an object with a camera when itapproaches a 360° end stop;

5. overcoming the problem of pan/tilt camera control when zoomed out;

6. controlling the camera to move rapidly between two or more views ofinterest; and,

7. VCR management issues including: failure of VCRs; change-over delayin VCR cassettes; and dealing with camera failure and replacement.

It is to be kept in mind that the purpose of the video security systemof the present invention is to provide video images regarding eventspertaining to the security of a building or the like and to allow thoserecorded video images to be presentable in a court of law as irrefutableevidence of the events which took place.

Hereinafter the term "VCR" ill be used to denote any form of videosignal recording and/or playback device (referred to as a "VRD") and mayinclude a video cassette recorder, or any optical or digital recordingmedia suitable for recording video signals.

BACKGROUND OF THE INVENTION

1. "Text Overlay"--In the field of video security systems it is known tointroduce text into the video signal to provide a real time record ofthe details of the event which is being monitored. A disadvantage ofsuch prior art systems is that the information is introduced into thevideo part of the video signal and hence over-writes a part of the videopicture which would have otherwise been recorded.

The present invention overcomes this by inserting the text into thenon-video part of the video signal

2. "Toggle"--The secret to the success of switching between a pluralityof fixed locations is to be able to quickly and easily identify two, ormore, viewing locations "on the fly". This is particularly for viewingtargets of short term or temporary interest.

In the context of the present invention "on the fly" means to beperformed whilst the VSS is in its normal mode of operation and withoutinterrupting the normal operation of the VSS.

Also, in the context of the present invention the feature of "switchingback and forth between two (or more) viewing locations" is referred toas "toggling" between the viewing locations.

However, where the operator is interested in two or more specificlocations within the viewing region the PTZ camera must be adjustedmanually between these locations. This is quite laborious and tediousfor the person operating the PTZ camera since it involves adjusting thepan, tilt, zoom and focus setting for the PTZ camera.

We have discovered that this can be overcome by recording the PTZ camerasettings corresponding to the desired locations of viewing into a cameraposition controller and switching between the locations by recalling thesettings for each of the viewing locations. The PTZ camera then iscontrolled by the camera position controller to adjust itself betweenthe desired locations.

"Preset" PTZ camera viewing locations are known and are widely used,however, they require the operator to make several control operations toset each viewing location and at least two control operations to switchfrom one viewing location to another.

This is particularly inconvenient in a viewing region such as in acasino where there are many potential targets, where there is arequirement to quickly and reliably set viewing locations and where itis critical to be able to switch between typically two targets. The twotargets would typically be a suspected felon and a handbag which it issuspected that the felon will steal. Typically, there is an accompliceto be monitored as well. Usually the accomplice in this scenario is awoman who collides briefly with the felon and takes the handbag once thehandbag has been stolen. Hence, the task of the operator of the VSS isto first monitor the suspected felon and the handbag by toggling backand forth between the two and once the handbag has been stolen tomonitor the felon and then to monitor a person who may collide with thefelon.

In the present invention we have determined a way to enable the operatorto operate a single control function (such as by a control button) toset, update and toggle between two or more viewing locations. This mostreliably and efficiently allows the operator to monitor the targets.

3. "Signal Equalisation"--Prior art video security systems have theproblem that equalisation of the video signals must be provided for eachvideo camera. That is, there must be one equalisation unit for eachcamera.

We have overcome this difficulty by having one equalisation unit foreach video monitor and automatically adjusting the equalisation unit foreach video camera as it is connected to the monitor. Hence, only afraction of the number of equalisation units is required.

4. "Rotation End Stops"--Another problem of existing video securitysystems is that most of the cameras which they use are only able torotate through about 360°. Hence, when following a target the camera canreach its end stops and have to unwind before it can continue to followthe target. By the time that the camera has unwound the target may nolonger be in sight.

We have overcome this problem in an inexpensive way by using a cableloop wound in a way that it is able to twist 3 to 4 times, and hence thecamera can be rotated through an angle of about 1000°. A control unit ofthe camera then is programmed to return the camera to about the centreof its rotation when the camera is not being used to track a target.Hence, the camera is relatively unlikely to reach its end stops duringnormal use.

5. "Pan Speed vs Zoom"--Prior art vide cameras have the further problemthat when the lens is zoomed in (that is viewing an object at adistance) the rate of pan per degree of arc is the same as when the lensis zoomed out. Hence, it becomes difficult to accurately control the panof the lens when zoomed in. Also, it is difficult to observe the imageof the camera during panning when zoomed in because it is usuallyblurred or indistinct due to the pan speed being too high.

We have overcome this problem by linking the pan speed to the zoomposition of the lens so that the rate of pan per degree of arc decreasesas the lens is zoomed in and increased as the lens is zoomed out.

6. "Accuracy of Camera Positioning"--Conventional camera positioncontrollers have problems in maintaining accuracy of positioning of thevideo camera (for viewing a target in a predetermined location) whilstseeking maximum speed of movement of the video camera. That is, in therace for maximum speed, so that one camera can be used to monitor two ormore locations, the position controller is not able to keep accuraterecord of the location of the camera. This is primarily due to problemsencountered in rapid changes in acceleration.

We have overcome this problem by designing a camera position controllerwhich ensures that there is a minimum period of substantially zeroacceleration before any change in acceleration direction. This thusavoids large changes in momentum introduced when switching abruptly fromacceleration to deceleration.

7. "Non-Recording Time"--Another problem of prior art video securitysystems is that during the times referred to in item 7 of the Field ofthe Invention no recording can occur. Hence, the video security systemcan not record all events which its cameras see. For example, in a videosecurity system having 125 VCRs there would be a minimum recording timeloss of 2 hours per day due only to the time taken to change over tapes(assuming the operation takes 30 seconds and each tape records for 8hours). There is further loss of recording when an operator deliberatelytakes a VCR off-line in order to review one of the tapes.

In order to overcome these periods of lost recording we have designed aVSS to automatically manage the VCRs and cameras so as to ensure thateach target is monitored continuously and each video signal is recordedcontinuously. This is achieved by using backup video cameras and backupVCRs and by providing a log of the camera and VCR associated with eachviewed target.

SUMMARY OF THE INVENTION

Therefore it is an object of the present invention to provide a videosecurity system to overcome the above identified problems.

1. It is an object of the present invention to provide a text insertionsystem which enables storage of text other than in the part of the videosignal which corresponds to the video image.

In accordance with another aspect of the present invention there isprovided a text insertion system for a video security system having avideo camera and a video monitor and/or a VRD capable of operation in arecord mode, the text insertion system comprising:

a text insertion means connected between the video camera and the videomonitor and/or VRD for inserting a text signal into a video signalreceived from the video camera for display on the video monitor and/orrecordal by the VRD, the insertion of the text signal being timed withinthe back porch of the video signal so that the text signal does notalter the visible part of the video frame of the video signal;

a control means connected to the text insertion means, the control meansgenerating the text signal and sending the text signal to the textinsertion means; and,

a playback means operatively associated with the text insertion meansand the control means, the playback means responding to the text signalportion of the video signal, the playback means having a text signaldisplay means for rendering the text signal visible on the videomonitor, and a text signal hiding means for rendering the text signalnon-visible on the video monitor, the text signal display means and thetext signal hiding means being operable by a person using the textinsertion system to allow alternating between showing text correspondingto the text signal on the video monitor and showing on the video monitorthat part of the video frame which would otherwise be obscured by thetext, and the playback means being able to make the text signal visibleor hidden during both recording and playback modes of operation of theVRD.

2. Therefore, it is an object of the present invention to provide a PTZcamera for a video security system which is capable of being controlledby an operator to toggle between a plurality of desired camera viewinglocations.

In accordance with one aspect of the present invention there is provideda PTZ camera for viewing a plurality of targets within a regionsurrounding the PTZ camera, the PTZ camera comprising:

a video lens and camera for viewing the targets and sending a videosignal to a video monitor and or a VRD;

a zoom control means for controlling the video lens for viewing thetargets;

a focus control means for focusing the video lens for viewing thetargets;

a pan control means for panning the video lens and camera for viewingthe targets;

a tilt control means for tilting the video lens and camera for viewingthe targets; and,

a camera position control means for controlling the video lens, the zoomcontrol means, the focus control means, the pan control means and thetilt control means, the camera position control means having a firstcurrent position means for storing the settings corresponding to thelocation of one of the targets, and a second current position means forstoring the settings corresponding to the location of another one of thetargets, the camera position control means being operable to switchcontrol between the first current position means and the second currentposition means for allowing viewing to switch between two targets ofpresent interest, wherein the first current position means and thesecond current position means are operatable to set, update and togglethe view on the video monitor between the two locations of the targets.

3. It is an object of the present invention to provide a transmissioncable equalisation system for a video security system having a pluralityof video cameras and a video monitor and/or a VRD capable of operationin a record mode, the transmission cable equalisation system comprising:

a selector means connected between the video cameras and the videomonitor and/or VRD for selecting video signals from the video cameras tobe directed to the video monitor and/or VRD so that the video signalfrom one video camera is display on the video monitor and/or recorded onthe VRD at a time;

an equaliser means connected between the selector means and the videomonitor and/or VRD for equalising the video signal from losses caused bythe nature of the connection between each of the video cameras and theselector means; and,

a control means connected to the equaliser means and the selector means,the control means having a reference means having data quantifying thelosses between each video camera and the selector means, and the controlmeans controlling the equaliser means to compensate for the lossesassociated with each video camera as its video signal is displayed onthe video monitor and/or recorded on the VRD so that the condition ofthe video signal at the video monitor and/or VRD is equalisedsubstantially independent of the characteristics of the connectionbetween the video camera and the selector means so that only oneequalisation means is required per video monitor and/or VRD instead ofone equalisation means per video camera.

4. It is an object of the present invention to provide a video camerawhich is controllable to rotate through a fixed angle which is greaterthan 360°.

In accordance with a still further aspect of the present invention thereis provided a video camera for a video security system, the video cameracomprising:

a video lens for viewing a target and sending a video signal to a videomonitor and/or a VRD;

a transport mechanism upon which the video lens is mounted, thetransport mechanism being rotatable through a fixed azimuth range ofgreater than 360° so that the video lens can view targets which movethrough an azimuth range of greater than 360°, and,

a loop of electrical cables arranged to be able to twist through anazimuth range of greater than 360°.

5. It is an object of the present invention to provide a video camerawhich is controllable to pan at a speed which changes corresponding tothe zoom setting of the camera.

In accordance with yet another aspect of the present invention there isprovided a video camera comprising:

a video lens for viewing a target and sending a video signal to a videomonitor and /or a VRD;

a zoom control means for controlling the video lens to see targets atvarying ranges from the video camera;

a pan control means for panning the video lens; and,

a control means for controlling the speed at which the video lens ispanned, the control means being able to set a relatively slow pan speedwhen the zoom control means controls the video lens to view a targetwhich is relatively far from the video lens and to set a relatively highpan speed when the zoom control means controls the video lens to view atarget which is relatively close to the video lens so that both distantand close targets can be panned over at substantially the same speed.

6. It is an object of the present invention to provide a cameratransport mechanism which has a camera position control system formoving a camera rapidly between a plurality of viewing positions.

In accordance with a further aspect of the present invention there isprovided a camera transport mechanism for moving a video camera betweena plurality of viewing positions, the camera transport mechanismcomprising:

a platform for carrying a video camera;

a vertical axis drive unit attached to the platform for moving platformabout a vertical axis;

a horizontal axis drive unit attached to the platform for moving theplatform about a horizontal axis; and,

a camera position control system for recording the location of aplurality of viewing positions and for controlling the movement of theplatform between said viewing positions, the camera position controlsystem being configured control the movement of the platform so as toprovide a minimum period during which there is substantially zeroacceleration between changes in acceleration of the platform fromacceleration to deceleration so as to reduce the amount of rate ofchange of momentum experienced by the platform and thus improve theaccuracy of determination of the position of the platform so as to moreaccurately control the movement of the platform and hence the videocamera between the viewing positions.

7. It is an object of the present invention to provide a video camerasubstitution system for ensuring that video images are always availableto be reviewed and/or recorded even in the event of the failure of avideo.

In accordance with a still further aspect of the present invention thereis provided a video camera substitution system for a video securitysystem having a fixed video camera for viewing a target area, a pan-tiltvideo camera capable of orientation to substantially view the saidtarget area and a video monitor and/or VCR capable of operation in arecord mode, the video camera substitution system comprising:

a failure detection means for detecting failure of the fixed videocamera;

a camera preset means having data concerning the position of the targetarea with respect to the pan-tilt video camera; and,

a control means in operative association with the failure detectionmeans, the camera preset means and the pan-tilt video camera, thecontrol means being capable of controlling the pan-tilt video camera formoving and setting the pan-tilt video camera to monitor the target areawhen the failure detection means detects failure of the fixed videocamera so that the target are a is monitored substantially continuously.

It is an object of the present invention to provide a video recordersubstitution system for ensuring that video images a nd al ways recordedeven in the event of the failure of a video recorder including failureto record due to changeover of recording media and taking the videorecorder out of service.

In accordance with a still further aspect of the present invention thereis provided a video recorder substitution system for a video securitysystem comprising:

a first VRD for recording a video signal corresponding to a target area;

a second VRD also capable of recording the video signal corresponding tosaid target area;

a record failure detection means for detecting failure of the first VRDto record said video signal, including failure due to change-over ofrecording media and due to taking the video recorder out of record itsmode of operation; and,

a control means in operative association with the record failuredetection means, with the first VRD and with the second VRD, the controlmeans being capable of controlling the second VRD to set the second VRDto record said video signal in the event that the record failuredetection means detects failure of the first VRD so that the videosignal corresponding to the target area is recorded substantiallycontinuously.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the present invention will now be describedwith reference to the accompanying drawings in which.

FIG. 1A is block diagram of a video security system in accordance withthe present invention;

FIG. 1B is a set of waveforms showing the nature of insertion of asignal corresponding to text into the video signal;

FIG. 2 is a block diagram of an automatic VCR management system inaccordance with the present invention;

FIG. 3 is block diagram of a text insertion system in accordance withthe present invention;

FIG. 4A is a block diagram of a prior art transmission cableequalisation system;

FIG. 4B is a block diagram of a transmission cable equalisation systemin accordance with the present invention;

FIG. 5 is a block diagram of a video camera substitution system inaccordance with the present invention; and,

FIG. 6 is a perspective view of a PTZ camera in accordance with thepresent invention, shown with part of its housing shown in phantom.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) Video SecuritySystem

In FIG. 1 there is shown a Video Security System (VSS) 10 comprising anAutomatic VCR Management System (AVCRMS) 12, a Text Insertion System(TIS) 14, a Transmission Cable Equalisation System (TCES) 16 and a VideoCamera Substitution System (VCSS) 18.

The VSS 10 also comprises a plurality of fixed position cameras 20, aplurality of pan-tilt cameras 22, a plurality of video monitors 24, aplurality of VCRs 26, one or more standby VCRs 28 and a printer 30.

Typically, the VSS 10 is embodied in a computer system programmed toeffect various routines equivalent to the systems 12, 14, 16 and 18described herein.

Automatic VCR Management System

As shown in FIG. 2 the AVCRMS 12 comprises a controller 40 and aselector 42.

Typically the controller 40 is in the form of a computer programmed toeffect certain control functions as described herein. The controller 40is connected to a remote control input 44 of each of the plurality ofVCRs 26 and 28 and to an alarm output 46 of each of the VCRs 26 and 28.The controller 40 being capable of operating each of the VCRs 26 and 28via the remote control inputs 44 and also being capable of sensing analarm condition in each of the VCRs 26 and 28 via the alarm outputs 46.The controller 40 disabling any one of the VCRs 26 and 28 upon theoccurrence of an alarm signal at the alarm output 46 of that VCR 26 or28. The alarm condition becomes active when the VCR 26 or 28 is nolonger in a record mode of operation. This can happen due to failure ofthe VCR 26 or 28, the VCR 26 or 28 being taken out of service such as tochange a recording tape or to review a recorded tape or for repairs orthe like.

The selector 42 is typically in the form of a matrix video switch inwhich any of its inputs 48 can be connected to any of its outputs 50, 52and 54. The output 50 is connected to one of the monitors 24, and theoutputs 52 and 54 are connected to record input 56 of two standby VCRs28. Each of the VCRs 26 and 28 has a play output 58 which is connectedto one of the video inputs of the selector 42 so that any video signalon any of the VCRs 26 or 28 can be displayed on the monitor 24. Theselector 42 is also connected via its inputs 48 to a plurality a videocamera outputs 60.

Typically, when one of the VCRs is detected as no longer being in arecord mode of operation the controller 40 causes an audible tone to begenerated and an alarm message is caused to be displayed on the monitor24. The message identifies which one of the VCRs 26 and 28 requiresattention. The controller 40 simultaneously selects the next availableone of the standby VCRs 28 and sets it to a record mode of operation viathe remote control input 44 and controls the selector 42 to direct thevideo signal from the relevant video camera output 60 to that VCR 28 forrecordal. The controller 40 also displays the identity of the videocamera and the VCR 28 onto which the video signal is now being recorded.Simultaneously, this information, along with the time and date and anyother special messages, are printed out on the printer 30.

Text Insertion System

As shown in FIGS. 2 and 3 the text inserter 14 is connected between thecamera outputs 60 and the inputs 56 of the VCRs 26. The text inserter 14is controlled by the controller 40 for the generation of text to beinserted into the video signal being recorded onto the VCR 26. Thecontroller 40 controls the insertion of the text into the video signalat a location which is not ordinarily part of the visible part of thevideo screen once displayed. Typically, the text data is inserted intothe horizontal line interval portion of the video signal (known as the"back porch" of the video signal).

The text inserter 14, particularly as shown in FIG. 3, inserts the textgenerated by the controller 40 into the video signal and is recordedonto the VCR 26 during recording. Due to the positioning of the textinto the video signal the text does not overly the normal viewableportion of the video signal. During playback of the video signal fromthe VCR 26 the text inserter extracts the text from the horizontal lineinterval of the video signal and reinserts it into the visible portionof the video signal so that the text can be seen on the monitor 24.

In the event that the text masks important parts of the video image onthe monitor 24 the text inserter 14 can be controlled by the controller40 to remove the text signal from the visible part of the video signal.Hence, the text recorded with the video image from the video cameras canbe removed from the video image seen on the monitor in the event that itmasks important parts of the video image.

It is important to note that the text is a data stream and not a videostream.

The recorded information can include time, date, source, equalisation,operator identification number, VCR identification number (since eachVCR has its own effective "fingerprint") and the like. This informationis important in the scheme of irrefutably proving that the imagesrecorded by the VCRs are the events which actually took place.

Transmission Cable Equalisation System

As shown in FIGS. 1, 4a and 4b the transmission cable equaliser 16 isconnected between the video camera output 60 and the text inserter 14and is controlled by the controller 40.

The controller 40 has a conditioning signal (such as data) whichcharacterises the nature of the connection between each of a pluralityof video cameras 70 and the selector 42. This conditioning signal takesinto account any losses in the connection between the camera 70 and theselector 42 due to the nature of a connecting cable including itstransmission characteristics and its length. The conditioning signal isapplied to the equaliser 16 so as to alter the gain of the equaliser 16to allow for the losses inherent in the cable of each of the cameras 70.

Hence, only one equaliser 16 is required per monitor 24 rather than oneequaliser 16 per camera 70. In the event that a new camera 70 is addedto the video security system 10 the equalising requirements for thatcamera 70 are input into the controller 40 for controlling the equaliser16 when video signals from that camera 70 are being viewed on themonitor 24.

Video Camera Substitution System

The cameras 70 in the video security system 10 include fixed positioncameras 70a and pan/tilt cameras 70b (herein referred to as PTZ cameras70b). Typically, a plurality of the fixed position cameras 70a aredirected at fixed targets in an area and a lesser number of the PTZcameras 70b are spread out amongst the fixed position cameras 70a sothat the PTZ cameras 70b can substantially view the same field as theplurality of fixed position cameras 70a and to be used to view movingtargets.

The video camera substitution system 18 is a part of the controller 40and has information concerning the relative positions of the PTZ cameras70b and the fixed position cameras 70a. The information includes whichof the PTZ cameras 70b are capable of covering the viewing areas of eachof the fixed position cameras 70a. The controller 40 is connected to thePTZ cameras 70b via a communication control module 74 so that in theevent that a particular one of the fixed position cameras 70a ceases tooperate the controller can automatically determine which one of the PTZcameras 70b can be used in its place and then control the PTZ camera 70bvia its controller 76 to pan, tilt, zoom and focus to view the targetviewed by the camera 70a which failed.

The VCSS 18 also has a keyboard 78 connected to the controller 40 forallowing manual operation of the PTZ cameras 70b to view targets at thewill of an operator of the keyboard 78. For this purpose the keyboard 78conveniently includes a joy stick 80.

Multiple Rotation Video Camera

The PTZ cameras 70b comprise a conventional camera 100 set on atransport mechanism 102 which is capable of rotating greater than 360°such as about 1000°.

The camera 100 has a lens 110 which has a zoom facility and whose iriscan be adjusted for changes in lighting levels.

The transport mechanism 102 has a housing 120, a frame 122, a verticalaxis drive unit 124, a horizontal axis drive unit 126 and control unit128.

The housing 120 comprises a ceiling mount 140, a camera mask 142 and atransparent cover 144.

The ceiling mount 140 is typically fixed into a ceiling of a building(although it could be fixed to a wall or the like) so that the cameramask 142 and the transparent cover 144 are disposed below the ceilingfor allowing the camera 100 viewing within a room under the ceiling. Theceiling mount 140 is typically made from anodised aluminium and istypically cylindrical in cross-section.

The camera mask 142 is attached to the frame 122 and hence is able torotate with respect to the ceiling mount 140. The camera mask 142 has aslot 150 which is dimensioned to allow the lens 110 to have a clearuninterrupted view through it. The slot 150 extends substantially from ahorizontal position with respect to the lens 110 to a verticallydownward position with respect to the lens 110. Hence, the lens can bemoved from a horizontal viewing position to a vertically downwardviewing position in the slot 150. The camera mask 142 has a plurality oflugs 152 for use in releasably attaching the camera mask 142 to clips154 of two mask mounts 156 (one of which is shown) of the frame 122.

Typically, the camera mask 142 is coloured black so as to avoidreflecting light from it. The purpose of the camera mask 142 is torotate with the camera 100 to mask observation of the viewing positionof the camera 100. We have discovered that due to the darkness of thecamera mask 142 the viewing position of the camera 100 is substantiallyunobservable.

The transparent cover 144 is attached to the ceiling mount 140 andlocated outside of the camera mask 142. The purpose of the transparentcover 144 is to shield the camera 100 and the interior of the transportmechanism 102 from the elements. In this manner the cover 144 can behermetically sealed to the ceiling mount 140 and the PTZ camera 70b canbe located out doors.

The frame 122 comprises a top plate 160, two brackets 162 and 164 and amoveable platform 166. The top plate 160 is disposed horizontally and isable to rotate inside the housing 120. The brackets 162 and 164 arefixed to the top plate 160 and disposed vertically downwardly therefrom.The platform 166 is conveniently substantially U-shaped and pivotablyattached to lower ends of the brackets 162 and 164. The pivotableattachment is via a pivot bolt 170 located through the bracket 162 and apivot axle 172 located through the bracket 164. The platform 166 has aplurality of fixing slots 176 for mounting the camera 100 onto it. Thefixing slots 176 are typically disposed parallel to the brackets 162 and164.

The vertical axis drive unit 124 comprises a drive motor 180 with adrive cog 182, a toothed cog 184 and a toothed belt 186. The toothed cog184 is releasably secured to the ceiling plate 140, such as by holes(not shown) in a top 188 of the toothed cog 184. The drive motor 180 isattached to the top plate 160 of the frame 122. The drive motor 180 isdriven by electrical signals from the control unit 128 for producingrotation of the drive cog 182. Since the toothed cog 184 is stationarywith respect to the ceiling mount 140 rotation of the drive cog 182causes the frame 122 to rotate within the housing 120. The speed ofrotation of the frame 122 is dependent upon the speed of the drive cog182 and the angle of rotation is dependent upon the time for which thedrive motor 180 receives signals from the control unit 128.

The horizontal axis drive unit 126 comprises a drive motor 200 with adrive cog 202, a toothed cog 204 and a toothed belt 206. The toothed cog204 is fixed to the platform 166 so that rotation of the toothed cog 204produces pivoting of the platform 166. The drive motor 200 is mountedonto the bracket 164 and the drive cog 202 drives the toothed belt 206for driving the toothed cog 204. The toothed cog 204 has a stop 210located in it for limiting the pivotable travel of the platform 166 soas to protect the camera 100 from damage which may otherwise occur. Thedrive motor 200 is controlled by signals from the control unit 128 forpivoting the lens 110 of the camera 100 in the slot 150 of the cameramask 142 as indicated by arrow 212. Typically, the horizontal drive unit126 allows pivoting of the platform 166 from substantially horizontal tosubstantially vertical.

The control unit 128 has a horizontal control unit and a verticalcontrol unit. Each of the horizontal and vertical control units has aposition sensor device for determining the position of the toothed cogs204 and 184 respectively. Typically, the position sensor device is ahole located in the toothed cog 184, 204 and the control unit are ableto count up and down from the position of the holes for determining themovement of the cogs 184, 204.

We have discovered that in order to quickly move the camera 100 from oneviewing position to another, and to keep accurate count of the actualposition of the camera 100 there are some physical constraints whichmust be allowed for. Principally this involves controlling the drivemotors 180 and 200 so as not to exceed maximum rates of acceleration anddeceleration and not to exceed a maximum speed. Also, and mostimportantly, we have discovered that the drive motors 180 and 200 needto be controlled so as to have a period of substantially zeroacceleration between periods of acceleration and deceleration. This isrequired because otherwise there is a very large change in the momentumof the transport mechanism 102 required in switching from accelerationto deceleration. The result of such abrupt changes in the accelerationof the transport mechanism is the control unit 128 looses count of theposition of the toothed cogs 184 and 204 and thus inaccuracies in thelocation of the camera 100 are experienced.

Hence, the control unit 128 is programmed to limit the maximum rate ofacceleration and deceleration of the drive motors 180 and 200 and toprovide a minimum period of substantially zero acceleration betweenperiods of acceleration and deceleration. The control unit 128 then usesthese limits to drive the transport mechanism 102 between viewinglocations whilst accurately reaching those viewing locations.

The PTZ camera 70b is, in one embodiment, connected to the remainder ofthe video security system 10 by a plurality of cables. The cables carryvideo signals, control signals and electrical power. In order to allowthe transport mechanism 102 to rotate through greater than 360° thecables are arranged in a loop so that they can be twisted three or fourtimes without damage. This allows the vertical axis drive unit 124 torotate the platform 166 through a total angle of about 1000°.

The control unit 128 has a counter to count up and down depending uponthe position and motion of the drive motor 180. Typically, the counterincrements the count by 4000 for each 360° of rotation. By such countingthe control unit 128 can be aware of how far the transport mechanism 102is away from its ultimate end of travel. The control unit 128 isprogrammed such that when the camera 100 is not engaged in tracking amoving event it unwinds to proximate the middle of its 1000° of angulartravel. In this way the chances of the transport mechanism 102 reachingits ultimate angular travel is greatly reduced.

In another embodiment slip rings are used for each cable, which thenallows the vertical axis drive unit 124 to rotate the platform 166through an infinite angle of rotation.

Hence, the PTZ camera 70b can be used to follow a target even where thetarget travels through an angle of greater than 360° and hence thechances of the PTZ camera 70b being run up against its limits ofrotation are greatly reduced and the ability to follow a target as itmoves through an area is greatly enhanced.

SWITCHING BETWEEN VIEWING LOCATIONS

The controller 40 controls the PTZ cameras 70b to move back and forthbetween a plurality of viewing locations so that the camera can monitora plurality of fixed locations.

The PTZ camera 70b comprises a video lens 110 and camera 100, a zoomcontrol, a focus control, a pan control, a tilt control and a cameraposition controller (included in the controller unit 128--FIG. 6).

The video lens and camera is settable to view a target. For example, thetarget could be a person at a gaming table in a casino. The video lenshas a machine readable signal corresponding to its zoom and focussetting. The zoom and focus controls allow adjustment of the zoom andfocus of the video lens and camera.

The pan and tilt controls control the pan and tilt of the video lens andcamera about substantially vertical and horizontal axes for viewingtargets typically in a region of 360° about the PTZ camera. The pan andtilt controls each have a machine readable signal corresponding to theirsettings.

The camera position controller is coupled to respond to the machinereadable signals from the video lens and camera, the zoom and focuscontrols and the pan and tilt controls. The camera position controllercontrols the settings of the video lens, the zoom and focus controls andthe pan and tilt controls for viewing the targets within the viewingregion automatically under the instruction of an operator.

The camera position controller has a first memory register (such aslocated in a computer) to store the values of the machine readablesignals corresponding to the settings of the video lens and camera, thezoom and focus controls and the pan and tilt controls. The first memoryregister stores the values of the settings corresponding to a firstlocation of temporary interest, such as the location of a handbag. Thecamera position controller also has a second memory register for storingthe values corresponding to a second location of temporary interest,such as the location of a suspected felon who is believed to be about tosteal the handbag.

The camera position controller has a toggle button which is operable tocause the values of the settings of the video lens and cameracorresponding to the second location to be recalled from the secondmemory register and loaded into the video lens and camera whilst thevalues corresponding to the first location are removed from the videolens and camera and stored into the first memory register. The togglebutton is also operable to cause the values of the settings to beupdated in the event that one of the targets moves or the operatorchooses a new target of temporary interest. The toggle button alsoallows for switching viewing between the two locations of temporaryinterest. By so doing the camera position controller can control thevideo lens and camera to view between two (or more) desired locationswithout continual manual re-adjustment of the video lens, the zoom andfocus controls or the pan and tilt controls.

In use, an operator can set a desired location of temporary interest tobe monitored by the video lens and camera. The video lens 110 and camera100 can then be manually moved to view another location of temporaryinterest and the video lens 110 and camera 100 can then by toggledbetween the two viewing locations by the operation of the toggle button.

To achieve this the operator first manually pans and tilts the videolens 110 and camera 100 to view a first target at a first location oftemporary interest. Then the operator manually adjust the zoom and focusof the video lens 110 and camera 100 for the target. The operator thenpresses the toggle button to store the values of the settings of thezoom and focus controls and the pan and tilt controls into the firstmemory register. The operator can then manually control the zoom andfocus controls and the pan and tilt controls for setting the video lens110 and camera 100 to view a second target at a second location oftemporary interest. When the operator again presses the toggle buttonthe values of the settings corresponding to the second location arestored into the second memory register and the values of the settingscorresponding to the first viewing location are recalled from the firstmemory register and used to control the video lens 110 and camera 100.Once the values are exchanged the camera position controller controlsthe zoom and focus controls and the pan and tilt controls to repositionthe viewing location of the video lens 110 and camera 100.

The location of the targets can be updated by manually adjusting thezoom and focus controls and the pan and tilt controls for the video lens110 and camera 100 and pressing the toggle button again to update thevalues stored in the relevant memory register. That is, when no manualadjustments are made to the settings of the video lens 110 and camera100 the toggle button causes toggling between the two locations oftemporary interest, but when manual adjustments are made to the settingsof the video lens 110 and camera 100 the toggle button causes updatingof the values of the settings.

Thus a PTZ camera can be used to monitor two fixed locations within aviewing area, as well as to operate under fully manual control. Hence,the PTZ camera of the present invention is the equivalent of two fixedposition cameras which can be set to view locations of temporaryinterest and which can be set to new locations of temporary interest asdesired by an operator. That is, the PTZ camera function as theequivalent of two dynamically positioned fixed cameras. Also, the changetime in changing between the two viewing locations is about the same asthe time involved in changing viewing between two fixed cameras (thatis, less than 1 second).

Typically, the camera position controller is configured to set the lastviewing position as being any position at which the operator stopped forgreater than, say, 1 second.

This facility could be configured into a logical data stack so that thelast, say 10, viewing positions could be stored in memory are recalledsequentially (this feature is herein referred to as "back up").

Modifications and variations such as would be apparent to a skilladdressee are considered within the scope of the present invention. Forexample, the camera position controller could have a single switch tocontrol toggling between two camera locations. Also, the iris setting ofthe video lens and camera could also be controlled.

We claim:
 1. A video recording system, comprising:a video camera forgenerating video signals; a first video recording unit for receiving andrecording the video signals from said video camera; a second videorecording unit for receiving and recording the video signals from saidvideo camera; and a controller connected to direct the video signalsfrom said video camera to at least one of said first video recordingunit and said second video recording unit, said controller generating alog indicating which of said first video recording unit and said secondvideo recording unit received the video signals from said video camerafor recording and the time period that said respective video recordingunit received the video signals from said video camera.
 2. The videorecording system according to claim 1, wherein the log generated by saidcontroller is a printed log.
 3. A video recording system, comprising:avideo camera for generating video signals; a primary video recordingunit for receiving the video signals from said video camera, saidprimary video recording unit further having a record mode of operationfor recording the video signals from said video camera; a back-up videorecording unit for receiving and recording the video signals from saidvideo camera; and a controller connected to sense when said primaryvideo recording unit is not in the record mode of operation, saidcontroller further directing the video signals from said video camera tosaid back-up video recording unit upon sensing that said primary videorecording unit is not in the record mode of operation.
 4. The videorecording system according to claim 3, wherein said primary videorecording unit generates an alarm signal when the primary videorecording unit is not in the record mode of operation, and wherein saidcontroller senses when said primary video recording unit is not in therecord mode of operation by sensing the alarm signal from said primaryvideo recording unit.
 5. The video recording system according to claim3, wherein said back-up video recording unit has a back-up unit recordmode of operation, and wherein said controller further places theback-up video recording unit into the back-up unit record mode ofoperation up on sensing when said primary video recording unit is not inthe record mode of operation.
 6. The video recording system according toclaim 3, wherein said controller further generates a log indicatingwhich of said primary video recording unit and said back-up videorecording unit received the video signals from said video camera forrecording and the time period that said respective video recording unitreceived the video signals from said video camera.
 7. The videorecording system according to claim 6, wherein the log generated by saidcontroller is a printed log.
 8. A video recording system, comprising:avideo camera for generating video signals; a primary video recordingunit for receiving the video signals from said video camera, saidprimary video recording unit having a record mode of operation forrecording of the video signals from said video camera; a plurality ofback-up video recording units for receiving the video signals from saidvideo camera, each of said plurality of back-up video recording unitshaving an available status when said respective back-up video recordingunit is available to record the video signals from said video camera;and a controller connected to sense when said primary video recordingunit is not in the record mode of operation, said controller furtherdirecting the video signals from said video camera to one of saidplurality of back-up recording units which is in the available statusfor recording upon sensing that said primary video recording unit is notin the record mode of operation.
 9. The video recording system accordingto claim 8, wherein said primary video recording unit generates an alarmsignal when the primary video recording unit is not in the record modeof operation, and wherein said controller senses when said primary videorecording unit is not in the record mode of operation by sensing thealarm signal from said primary video recording unit.
 10. The videorecording system according to claim 8, wherein each of said plurality ofback-up video recording units has a back-up unit record mode ofoperation, and wherein said controller places the one of said pluralityof back-up video recording units receiving the video signals from saidvideo camera into the back-up unit record mode of operation upon sensingwhen said primary video recording unit is not in the record mode ofoperation.
 11. The video recording system according to claim 8, whereinsaid controller further generates a log indicating which of said primaryvideo recording unit and said plurality of back-up video recording unitsreceived the video signals from said video camera for recording and thetime period that said respective video recording unit received the videosignals from said video camera.
 12. The video recording system accordingto claim 11, wherein the log generated by said controller is a printedlog.
 13. The video recording system according to claim 8, wherein eachof said plurality of back-up video recording units has a back-up unitrecord mode of operation, and wherein said controller senses when one ofsaid plurality of back-up video recording units receiving the videosignals from said video camera is not in the back-up unit record mode ofoperation directs the video signals intended for the one of saidplurality of back-up video recording units not in the back-up unitrecord mode of operation to the next available one of said plurality ofback-up video recording units.
 14. The video recording system accordingto claim 13, wherein each of said plurality of back-up video recordingunits generates a back-up alarm signal when the back-up video recordingunits is not in the back-up unit record mode of operation, and whereinsaid controller senses when each of said plurality of back-up videorecording units is not in the back-up record mode of operation bysensing the back-up alarm signal from the respective one of saidplurality of back-up video recording units.
 15. A video recordingsystem, comprising:a plurality of video cameras for generating videosignals; a plurality of primary video recording units for receiving thevideo signals from an associated one of said plurality of video cameras,each of said plurality of video recording units having a record mode ofoperation for recording the video signals from the associated one ofsaid plurality of video cameras; a back-up video recording unit forreceiving and recording the video signals from said plurality of videocameras; and a controller connected to sense when any particular one ofsaid plurality of primary video recording units is not in the recordmode of operation, said controller further directing the video signalsfrom the one of said plurality of primary video cameras associated withthe particular one of said plurality of primary video recording unitsthat is not in the record mode of operation to said back-up videorecording unit upon sensing that the particular one of said plurality ofprimary video recording units is not in the record mode of operation.16. The video recording system according to claim 15, wherein each ofsaid plurality of primary video recording units generates an alarmsignal when the respective primary video recording unit is not in therecord mode of operation, and wherein said controller senses when eachof said plurality of primary video recording units is not in the recordmode of operation by sensing the alarm signal from the respective one ofsaid plurality of primary video recording units.
 17. The video recordingsystem according to claim 15, wherein said back-up video recording unithas a back-up unit record mode of operation, and wherein said controllerplaces the back-up video recording unit into the back-up unit recordmode of operation upon directing video signals to said back-up videorecording unit.
 18. The video recording system according to claim 15,wherein said controller further generates a log indicating which of saidplurality of primary video recording units and said back-up videorecording unit received the video signals from each of said plurality ofvideo camera for recording and the time period that said respectivevideo recording unit received the video signals from the respective oneof said plurality of video cameras.
 19. The video recording systemaccording to claim 18, wherein the log generated by said controller is aprinted log.
 20. A video recording system, comprising:a plurality ofvideo cameras for generating video signals; a plurality of primary videorecording units for receiving the video signals from an associated oneof said plurality of video cameras, each of said plurality of videorecording units having a record mode of operation for recording thevideo signals from the associated one of said plurality of videocameras; a plurality of back-up video recording units for receiving thevideo signals from said plurality of video cameras, each of said back-upvideo recording units having means for placing it in an available statuswhen said respective back-up video recording unit is available to recordthe video signals from one of said plurality of video cameras; and acontroller connected to sense when any particular one of said pluralityof primary video recording units is not in the record mode of operation,said controller directing the video signals from the one of saidplurality of video cameras associated with the particular one of saidplurality of primary video recording units that is not in the recordmode of operation to one of said plurality of back-up video recordingunits being in the available status for recording upon sensing that theparticular one of said plurality of primary video recording units is notin the record mode of operation.
 21. The video recording systemaccording to claim 20, wherein each of said plurality of primary videorecording units generates an alarm signal when the respective primaryvideo recording unit is not in the record mode of operation, and whereinsaid controller senses when each of said plurality of primary videorecording units is not in the record mode of operation by sensing thealarm signal from the respective one of said plurality of primary videorecording units.
 22. The video recording system according to claim 20,wherein each of said plurality of back-up video recording units has aback-up unit record mode of operation, and wherein said controller hasmeans for placing the one of said plurality of back-up video recordingunits receiving the video signals from the one of said plurality ofvideo cameras associated with the primary video recording unit not inthe record mode of operation into the back-up unit record mode ofoperation.
 23. The video recording system according to claim 20, whereineach of said plurality of back-up video recording units has a back-upunit record mode of operation, and wherein said controller senses wheneach of said plurality of back-up video recording units is not in theback-up unit record mode of operation and directs the video signalsintended for the one of said plurality of back-up video recording unitsnot in the back-up unit record mode of operation to the next availableone of said plurality of back-up video recording units.
 24. The videorecording system according to claim 20, wherein each of said pluralityof back-up video recording units generates a back-up alarm signal whenan associated one of the back-up video recording units is not in theback-up unit record mode of operation, and wherein said controllersenses when each of said plurality of back-up video recording units isnot in the back-up record mode of operation by sensing the back-up alarmsignal from the respective one of said plurality of back-up videorecording units.
 25. The video recording system according to claim 20,wherein said controller generates a log indicating which of saidplurality of primary video recording units and said plurality of back-upvideo recording units received the video signals from each of saidplurality of video cameras for recording and the time period that saidrespective video recording unit received the video signals from saidrespective video camera.
 26. The video recording system according toclaim 25, wherein the log generated by said controller is a printed log.